Feshbach resonances in the F + H 2 O → HF + OH reaction

Transiently trapped quantum states along the reaction coordinate in the transition-state region of a chemical reaction are normally called Feshbach resonances or dynamical resonances. Feshbach resonances trapped in the HF–OH interaction well have been discovered in an earlier photodetchment study of FH2O−; however, it is not clear whether these resonances are accessible by the F + H2O reaction. Here we report an accurate state-to-state quantum dynamics study of the F + H2O → HF + OH reaction on an accurate newly constructed potential energy surface. Pronounced oscillatory structures are observed in the total reaction probabilities, in particular at collision energies below 0.2 eV. Detailed analysis reveals that these oscillating structures originate from the Feshbach resonance states trapped in the hydrogen bond well on the HF(v′ = 2)-OH vibrationally adiabatic potentials, producing mainly HF(v′ = 1) product. Therefore, the resonances observed in the photodetchment study of FH2O− are accessible to the reaction. Feshbach resonances are transiently trapped states along a reaction coordinate, providing a probe to the reaction’s potential energy surface (PES) but difficult to analyze in polyatomic systems. Here the authors identify Feshbach resonances in a reacting 4-atom system by state-to-state quantum dynamics using a full-dimensional PES.